Turbocharger, notably for a combustion engine

ABSTRACT

Turbocharger comprising a shaft, a housing, a turbine wheel and a compressor wheel mounted onto the shaft, at least one rolling bearing located between the shaft and the housing and comprising an inner ring, an outer ring and at least one row of rolling elements between raceways provided on the rings. 
     Said turbocharger comprises at least one intermediate sleeve radially located between the shaft and the inner ring of the rolling bearing.

CROSS-REFERENCE TO RELATED APPLICATION

This United States Non-Provisional Utility application claims the benefit of priority to copending European Patent Application No. 11306085.9, filed on Aug. 30, 2011, which is incorporated herein in its entirety.

FIELD OF THE INVENTION

The present invention relates to the field of turbochargers, and in particular those used in combustion engines for automotive vehicles.

BACKGROUND OF THE INVENTION

In such application, a turbocharger is used to enhance the combustion engine performance by blowing compressed air into the cylinders of said engine.

A turbocharger generally comprises a housing, a shaft extending through an opening formed on the housing, a turbine wheel mounted on a first end portion of the shaft and located in an exhaust gases passage of the combustion engine, a compressor wheel mounted on an opposite second end portion of said shaft and located in an admission gases passage of the engine, and rolling bearings disposed between the shaft and the housing. When the turbine wheel is rotated by the flow of the exhaust gases, the shaft and the compressor wheel are rotated which leads to a compression of the admission gases introduced into the cylinders of the combustion engine.

However, in order to disassemble the rolling bearings from the shaft, an axial load is generally applied to the shaft, which may lead to indentations on the raceways of the rolling bearings. The damaged rolling bearings have thus to be replaced.

Replacing the rolling bearings after all disassembly procedures leads to an increase of the mounting cost.

One aim of the present invention is therefore to overcome the aforementioned drawbacks.

SUMMARY OF THE INVENTION

It is a particular object of the present invention to provide a turbocharger which is simple to manufacture and economic while guaranteeing a disassembly of the rolling bearings without damaging the rolling bearings or the shaft.

In one embodiment, the turbocharger comprises a shaft, a housing, a turbine wheel and a compressor wheel mounted onto the shaft, at least one rolling bearing located between the shaft and the housing and comprising an inner ring, an outer ring and at least one row of rolling elements between raceways provided on the rings.

The turbocharger comprises at least one intermediate sleeve radially located between the shaft and the inner ring of the rolling bearing.

The intermediate sleeve between the rolling bearing and the shaft allows the shaft to be disassembled without damaging the rolling bearing.

Advantageously, the intermediate sleeve comprises at least one end axially extending further than the radial lateral surface of the inner ring of the rolling bearing. The end of the sleeve, extending axially further than the radial lateral surface of the inner ring, further referenced as a “first end”, allows the sleeve to cooperate with an external mounting tool.

Preferably, the at least one end called “the first end” of the intermediate sleeve is provided with at least one positioning means adapted to cooperate with an external tool, such as an extractor or a hub puller.

The positioning means may comprise at least one annular groove, at least one threaded portion, at least one radial hole or opening or a radial through-hole or through-opening, made through the thickness of the intermediate sleeve.

The intermediate sleeve may comprise at least one axial slot provided axially on all its axial length.

Preferably, the intermediate sleeve has a stepped bore adapted to cooperate with a stepped outer cylindrical surface of the shaft. One end of the intermediate sleeve, opposite to the first end, may comprise a shoulder, for axially retaining the rolling bearing.

In one embodiment, the turbocharger comprises a second rolling bearing mounted radially between the intermediate sleeve and the housing and comprising an inner ring, an outer ring and at least one row of rolling elements between said rings.

In another embodiment, the intermediate sleeve comprises a first cylindrical portion in contact with the inner ring of the first rolling bearing, a second cylindrical portion having a diameter bigger than the diameter of the first cylindrical portion for retaining axially the first inner ring and a third cylindrical portion having a toroidal surface forming an inner ring of a second rolling bearing comprising an outer ring and at least one row of rolling elements between said second outer ring and said toroidal surface of the sleeve.

Advantageously, the intermediate sleeve has a stepped bore adapted to cooperate with a stepped outer cylindrical surface of the shaft.

Preferably, the first outer ring and the second outer ring form one unique outer ring.

The intermediate sleeve can be made of a metallic material, such as 10006, DC03 or Aluminium alloy.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention and its advantages will be better understood by studying the detailed description of specific embodiments given by way of non-limiting examples and illustrated by the appended drawings on which:

FIG. 1 is an axial section of a turbocharger according to a first embodiment of the invention;

FIG. 2 is an axial section of an intermediate sleeve of FIG. 1 according to another example;

FIG. 3 is a perspective view of an intermediate sleeve of FIG. 2 according to another example;

FIGS. 4, 5 a, 5 b, 6 a, 6 b are axial sections of intermediate sleeves showing other examples of the positioning means;

FIG. 7 is an axial section of a turbocharger according to a second embodiment of the invention;

FIG. 8 is an axial section of a turbocharger according to a third embodiment of the invention;

FIG. 9 is a perspective view of an intermediate sleeve of FIG. 8;

FIGS. 10 and 11 illustrate other examples of the positioning means of FIG. 8.

DETAILED DESCRIPTION OF THE INVENTION

As illustrated on FIG. 1, which illustrates an embodiment of a turbocharger 10 according to an example of the invention, the turbocharger 10 comprises a housing 11, a shaft 12 extending along an axial axis 12 a through a cylindrical bore 11 a or opening of the housing 11, two rolling bearings 13, 14 disposed into the bore 11 a, a turbine wheel 15 fixed at one end of the shaft 12, a compressor wheel 16 fixed at an opposite end of said shaft 12, and an intermediate sleeve 17 radially located between the shaft 12 and the rolling bearings 13, 14. The turbocharger 10 also comprises a cap 18 fixed at an axial end of the housing 11.

Each rolling bearing 13, 14 comprises an inner ring 13 a, 14 a and an outer ring 19 between which is housed two rows of rolling elements 13 b, 14 b, which in this case are balls, two annular cages 13 c, 14 c maintaining the circumferential spacing of the rolling elements 13 b, 14 b. The axis of each rolling bearing 13, 14 is coaxial with the axis 12 a of the shaft 12 of the turbocharger 10.

The inner rings 13 a, 14 a are concentric and symmetric with respect to a transverse radial plane passing through the centre of the outer ring 19. The rings 13 a, 14 a, 19 are of the solid type. A “solid ring” is to be understood as a ring obtained by machining with removal of material (by machining, grinding) from metal tube stock, bar stock, rough forgings and/or rolled blanks.

The outer ring 19, forming the outer ring of the first rolling bearing 13 and the outer ring of the second rolling bearing 14, comprises an outer cylindrical surface 19 a delimited by opposite radial lateral surfaces 19 b, 19 c which respectively axially come into contact with the cap 18 and a radial shoulder 11 b of the housing 11. As illustrated, a bushing 20 is mounted axially between the cap 18 and the radial lateral surface 19 b of the outer ring 19, in order to compensate an axial clearance between the cap 18 and said radial lateral surface 19 b. The outer ring 19 also comprises a bore 19 d of cylindrical shape from which are formed toroidal raceways (not referenced) having in cross-section a concave internal profile adapted to the rolling elements 13 b, 14 b. The raceways are symmetrical with respect to the transverse radial plane passing through the centre of the outer ring 19.

In the disclosed embodiment, the inner rings 13 a, 14 a are identical, symmetrical with respect to the transverse radial plane of symmetry of the outer ring 19 and mounted axially fixedly one against the other. Alternatively, the two inner rings 13 a, 14 a may form one unique inner ring having two raceways. Each inner ring 13 a, 14 a has a bore 13 d, 14 d of cylindrical shape into which the intermediate sleeve 17 is mounted. Said bore 13 d, 14 d is delimited respectively by opposite radial lateral surfaces 13 e, 13 f; 14 e, 14 f. The radial lateral surface 13 e of the inner ring 13 a of the first rolling bearing 13 is coplanar with the lateral surface 19 b of the outer ring 19 and axially bears against the compressor wheel 16 via a bushing 21 radially located the shaft 12 and the cap 18 and an annular spacer 22 mounted on the intermediate sleeve 17 axially between the inner ring 13 a of the first rolling bearing 13 and the bushing 21. The radial surface 14 f of the inner ring 14 a of the second rolling bearing 14 axially bears against a radial shoulder 12 b of the shaft 12. Each inner ring 13 a, 14 a also comprises an outer cylindrical surface 13 g, 14 g onto which first and second toroidal circular raceways (not referenced) are formed. The said raceways have in cross-section a concave internal profile adapted to the rolling elements 13 b, 14 d the said raceways being directed radially outwards. The raceways are symmetrical with respect to the transverse radial plane passing through the centre of the outer ring 19.

As shown on FIG. 1, the turbocharger 10 is further provided with a sealing ring 23 a mounted radially between the bushing 21 and the cap 18 and axially disposed between the compressor wheel 16 and the first rolling bearing 13, and with two sealing rings 23 b, 23 c disposed radially between the shoulder 12 b of said shaft 12 and the bore 1 la of housing 11 and axially mounted between the second rolling bearing 14 and the turbine wheel 15.

In the disclosed embodiment, the housing 11 comprises an axial cooling channel 11 c extending from a radial end surface of said housing 11 against which the cap 18 is mounted. The cooling channel 11 c extends axially further than the outer ring 19 of the rolling bearings 13, 14 and ends in the vicinity of a radial end surface of the housing 11 located on the turbine wheel 15 side. The cooling channel 11 c is closed by the cap 18. The cooling channel 11 c formed within the housing 11 is annular and radially surrounds the rolling bearings 13, 14. A cooling fluid (not shown), such as water, can be introduced into the cooling channel 11 c.

The housing 11 further comprises an axial drilling 11 d, acting as a lubricant reservoir, extending from a radial end surface of said housing 11 against which the cap 18 is mounted. The drilling 11 d ends in the vicinity of a radial end surface of the housing 11 located on the turbine wheel 15 side. The drilling 11 d formed within the housing 11 is annular and radially surrounds the rolling bearings 13, 14 and is provided with passages 11 e, 11 f made through the thickness of the housing 11. The passages 11 e, 11 f are adapted to cooperate respectively with a passage 19 e, 19 f made through the thickness of the outer ring 19 through which the lubricant contained in the drilling 11 d can flow by gravity towards the balls 13 b and 14 b.

As illustrated on FIG. 1, the intermediate sleeve 17 is of tubular shape and comprises a first end 17 a axially extending further than the radial lateral surface 13 e of the inner ring 13 a of the first rolling bearing 13 and a second end 17 b having a radial lateral surface (not referenced) coplanar with the radial lateral surface 14 f of the inner ring 14 a of the second rolling bearing 14. The intermediate sleeve 17 comprises a bore 17 c in contact with a cylindrical outer surface 12 c of the shaft 12.

The first end 17 a of the intermediate sleeve 17 is provided with a positioning means 24 adapted to cooperate with an external tool (not illustrated) used, for example in order to dissemble the shaft 12 from the intermediate sleeve 17. As illustrated on FIG. 1, the positioning means 24 comprises an annular groove 24 a provided on the outer cylindrical surface (not referenced) of the sleeve 17 located at the first end 17 a. The intermediate sleeve 17 can be made of a metallic material, such as 10006, DC03 or Aluminium alloy.

FIGS. 2 and 3 in which identical parts are given identical references, illustrates other examples of the intermediate sleeve 17 of FIG. 1.

As illustrated on FIG. 2, the first end 17 a comprises a positioning means 24, such as an annular groove 24 a and the second end 17 b of the intermediate sleeve 17, opposite to the first end 17 a, comprises a shoulder 17 d, in order to axially retain the inner ring 14 a of the second rolling bearing 14.

As shown in FIG. 3, the intermediate sleeve 17 comprises at the first end 17 a, a positioning means 24, such as an annular groove 24 a and an axial slot 17 e provided axially on all the axial length of the intermediate sleeve 17. In this embodiment, the intermediate sleeve 17 can be made, for example, of a metal sheet, stamped so as to form the axial slot 17 e. The axial slot 17 e allows the intermediate sleeve 17 to radially deform during a disassembly step, in order to disassemble the shaft 12 and the intermediate sleeve 17 easier.

FIGS. 4 to 6, in which identical parts are given identical references, illustrates other examples of the positioning means 24 of the intermediate sleeve 17 for an external tool.

The positioning means 24 of FIG. 4 comprises a threaded portion 24 b, adapted to cooperate with a threaded tool (not illustrated).

The positioning means 24 of FIGS. 5 a and 5 b comprise one radial hole 24 c, or radial through-hole 24 d made through the thickness of the intermediate sleeve 17. As an alternative, a plurality of holes 24 c or through-holes 24 d can be made radially on the first end 17 a of the intermediate sleeve 17 and act as positioning means 24 for an external tool.

The positioning means 24 of FIGS. 6 a and 6 b comprise one radial opening 24 e, of general oval shape, or radial through-opening 24 f made through the thickness of the intermediate sleeve 17. The diameter of the hole 24 c is smaller than the diameter of the opening 24 e. As an alternative, a plurality of radial opening 24 e or radial through-opening 24 f can be made radially on the first end 17 a of the intermediate sleeve 17 and act as positioning means 24 for an external tool.

In all examples illustrated on FIGS. 4 to 6, the second end 17 b of the intermediate sleeve 17 is provided with a shoulder 17 d. As an alternative, the second end 17 b can be provided with no shoulder, as shown in the example of FIG. 1.

As illustrated on the FIG. 7, which illustrates an embodiment of a turbocharger 30 according to an example of the invention, the turbocharger 30 comprises a housing 31, a shaft 32 extending along an axial axis 32 a through a cylindrical bore 31 a or opening of the housing 31, two rolling bearings 33, 34 disposed into the bore 31 a of the housing, a turbine wheel 35 fixed at one end of the shaft 32, a compressor wheel 36 fixed at an opposite end of said shaft 32, and a intermediate sleeve 37 radially located between the shaft 32 and the rolling bearings 33, 34. The turbocharger also comprises a cap 38 fixed at an axial end of the housing 31.

Each rolling bearing 33, 34 comprises an inner ring 33 a, 34 a and an outer ring 39 between which is housed two rows of rolling elements 33 b, 34 b, which in this case are balls, two annular cages 33 c, 34 c maintaining the circumferential spacing of the rolling elements 33 b, 34 b. The axis of each rolling bearing 33, 34 is coaxial with the axis 32 a of the shaft 32 of the turbocharger 30.

The inner rings 33 a, 34 a are concentric and symmetric with respect to a transverse radial plane passing through the centre of the outer ring 39. The rings 33 a, 34 a, 39 are of the solid type.

The outer ring 39, forming the outer ring of the first rolling bearing 33 and the outer ring of the second rolling bearing 34, comprises an outer cylindrical surface 39 a delimited by opposite radial lateral surfaces 39 b, 39 c which respectively axially come into contact with the cap 38 and a radial shoulder 31 b of the housing 31. As illustrated, a bushing 40 is mounted axially between the cap 38 and the radial lateral surface 39 b of the outer ring 39, in order to compensate an axial clearance between the cap 38 and said radial lateral surface 39 b. The outer ring 39 also comprises a bore 39 d of cylindrical shape from which are formed toroidal raceways (not referenced) having in cross-section a concave internal profile adapted to the rolling elements 33 b, 34 b. The raceways are symmetrical with respect to the transverse radial plane passing through the centre of the outer ring 39.

In the disclosed embodiment, the inner rings 33 a, 34 a are identical, symmetrical with respect to the transverse radial plane of symmetry of the outer ring 39 and mounted axially fixedly one against the other. Alternatively, the two inner rings 33 a, 34 a may form one unique inner ring having two raceways. Each inner ring 33 a, 34 a has a bore 33 d, 34 d of cylindrical shape into which the intermediate sleeve 37 is mounted. Said bore 33 d, 34 d is delimited respectively by opposite radial lateral surfaces 33 e, 33 f; 34 e, 34 f. The radial lateral surface 33 e of the inner ring 33 a of the first rolling bearing 33 is coplanar with the lateral surface 39 b of the outer ring 39 and axially bears against the compressor wheel 36 via a bushing 41 radially located the shaft 32 and the cap 18 and a spacer 42 mounted on the intermediate sleeve 37 axially between the inner ring 33 a of the first rolling bearing 33 and the bushing 41. The radial surface 34 f of the inner ring 34 a of the second rolling bearing 34 axially bears against a radial shoulder 32 b of the shaft 32. Each inner ring 33 a, 34 a also comprises an outer cylindrical surface 33 g, 34 g onto which first and second toroidal circular raceways (not referenced) are formed. The said raceways have in cross-section a concave internal profile adapted to the rolling elements 33 b, 34 d the said raceways being directed radially outwards. The raceways are symmetrical with respect to the transverse radial plane passing through the centre of the outer ring 39.

As shown on FIG. 7, the turbocharger 30 is further provided with a sealing ring 43 a mounted radially between the bushing 41 and the cap 38 and axially disposed between the compressor wheel 36 and the first rolling bearing 33, and with two sealing rings 43 b, 43 c disposed radially between the shoulder 32 b of said shaft 32 and the bore 31 a of housing 31 and axially mounted between the second rolling bearing 34 and the turbine wheel 35.

In the disclosed embodiment, the housing 31 comprises an axial cooling channel 31 c extending from a radial end surface of said housing 31 against which the cap 38 is mounted. The cooling channel 31 c extends axially further than the outer ring 39 of the rolling bearings 33, 34 and ends in the vicinity of a radial end surface of the housing 31 located on the turbine wheel 35 side. The cooling channel 31 c is closed by the cap 38. The cooling channel 31 c formed within the housing 31 is annular and radially surrounds the rolling bearings 33, 34 on its entire length. A cooling fluid (not shown), such as water, can be introduced into the cooling channel 31 c.

The housing 31 further comprises an axial drilling 31 d, acting as a lubricant reservoir, extending from a radial end surface of said housing 31 against which the cap 38 is mounted. The drilling 31 d ends in the vicinity of a radial end surface of the housing 31 located on the turbine wheel 35 side. The drilling 31 d formed within the housing 31 is annular and radially surrounds the rolling bearings 33, 34 and is provided with passages 31 e, 31 f made through the thickness of the housing 31. The passages 31 e, 31 f are adapted to cooperate respectively with a passage 39 e, 39 f made through the thickness of the outer ring 39 though which the lubricant contained in the drilling 31 d can flow by gravity towards the balls 33 b and 34 b.

As illustrated on FIG. 7, the intermediate sleeve 37 is of tubular shape and comprises a first end 37 a axially extending further than the radial lateral surface 33 e of the inner ring 33 a of the first rolling bearing 33 and a second end 37 b having a shoulder 37 d, in order to axially retain the inner ring 34 a of the second rolling bearing 34. The shoulder 37 d is axially in contact with the lateral radial surface 34 f of the inner ring 34 a of the second rolling bearing 34 and with the shoulder 32 b of the shaft 32. The intermediate sleeve 37 comprises a stepped bore 37 c in contact with a stepped outer cylindrical outer surface 32 c of the shaft 32. The intermediate sleeve 37 is thus in contact in three zones with the shaft 32, which allows to have a reduced surface dedicated to the centering function, which requires a high machining precision.

The first end 37 a of the intermediate sleeve 37 is provided with a positioning means 44 adapted to cooperate with an external tool (not illustrated) used, for example in order to dissemble the shaft 32 from the intermediate sleeve 37. The positioning means 44 comprises an annular groove 44 a on the first end 37 a of the intermediate sleeve 37.

As an alternative, positioning means 44 can be provided with a threaded portion, a hole or through-hole or with an opening or through-opening.

As illustrated on the FIG. 8, which illustrates an embodiment of a turbocharger 50 according to an example of the invention, the turbocharger 50 comprises a housing 51, a shaft 52 extending along an axial axis 52 a through a cylindrical bore 51 a or opening of the housing 51, two rolling bearings 53, 54 disposed into the bore 51 a of the housing, a turbine wheel 55 fixed at one end of the shaft 52, a compressor wheel 56 fixed at an opposite end of said shaft 52, and a intermediate sleeve 57 radially located between the shaft 52 and the rolling bearings 53, 54. The turbocharger 50 also comprises a cap 58 fixed at an axial end of the housing 51.

The first rolling bearing 53 comprises an inner ring 53 a, an outer ring 59 between which is housed a row of rolling elements 53 b,which in this case are balls, an annular cage 53 c maintaining the circumferential spacing of the rolling elements 53 b. The rings 53 a, 59 are of the solid type.

The outer ring 59, forming the outer ring of the first rolling bearing 53 and the outer ring of the second rolling bearing 54, comprises an outer cylindrical surface 59 a delimited by opposite radial lateral surfaces 59 b, 59 c which respectively axially come into contact with the cap 58 and a radial shoulder 51 b of the housing 51. As illustrated, a bushing 60 is mounted axially between the cap 58 and the radial lateral surface 59 b of the outer ring 59, in order to compensate an axial clearance between the cap 58 and said radial lateral surface 59 b. The outer ring 59 also comprises a bore 59 d of substantially cylindrical shape from which are formed toroidal raceways (not referenced) having in cross-section a concave internal profile adapted to the rolling elements 53 b, 54 a. The raceways are symmetrical with respect to the transverse radial plane passing through the centre of the outer ring 59.

The inner ring 53 a has a bore 53 d of cylindrical shape into which the intermediate sleeve 57 is mounted. Said bore 53 d is delimited respectively by opposite radial lateral surfaces 53 e, 53 f. The radial lateral surface 53 e of the inner ring 53 a of the first rolling bearing 53 is coplanar with the lateral surface 59 b of the outer ring 59 and axially bears against the compressor wheel 56 via a bushing 61 radially located the shaft 52 and the cap 58 and a spacer 62 mounted on the intermediate sleeve 57 axially between the inner ring 53 a of the first rolling bearing 53 and the bushing 61. The inner ring 53 a also comprises an outer cylindrical surface 53 g onto which a first toroidal circular raceway (not referenced) is formed. The said raceway has in cross-section a concave internal profile adapted to the rolling elements 53 b, the said raceway being directed radially outwards.

The intermediate sleeve 57, of tubular shape, illustrated in details in FIG. 9, comprises a first cylindrical portion 57 a in contact with the inner ring 53 a of the first rolling bearing 53 and axially extending further from the radial lateral surface 53 e of the inner ring 53 a, a second cylindrical portion 57 b, having a diameter bigger than the diameter of the first cylindrical portion 57 a, for retaining axially the first inner ring 53 a and a third cylindrical portion 57 c forming the inner ring of the second rolling bearing 54.

The first cylindrical portion 57 a, forming a first end of the intermediate sleeve 57, is radially in contact with the bore 53 d of the inner ring 53 a. The third portion 57 c of the intermediate sleeve 57, forming a second end of the intermediate sleeve 57, comprises a radial lateral surface 57 d which axially bears against a radial shoulder 52 b of the shaft 52 and an outer cylindrical surface (not reference) of cylindrical shape from which are formed a toroidal raceway 57 e having in cross-section a concave internal profile adapted to rolling elements 54 a of the second rolling bearing 54.

The intermediate sleeve 57 comprises a stepped bore 57 f in contact with a stepped outer cylindrical outer surface 52 c of the shaft 52. The intermediate sleeve 57 is thus in contact in three zones with the shaft 52. As an alternative, the bore 57 f of the intermediate sleeve 57 can be cylindrical in contact with a cylindrical outer surface of the shaft 52.

The second rolling bearing 54 comprises an outer ring 59, being the same outer ring as for the first rolling bearing 53, and a row of rolling elements 54 a, which in this case are balls between the third portion 57 c of the intermediate sleeve 57 and the outer ring 59, an annular cage 54 b maintaining the circumferential spacing of the rolling elements 54 a. The axis of each rolling bearing 53, 54 is coaxial with the axis 52 a of the shaft 52 of the turbocharger 50.

The first end 57 a of the intermediate sleeve 57 is provided with a positioning means 64 adapted to cooperate with an external tool (not illustrated) used, for example in order to dissemble the shaft 52 from the intermediate sleeve 57.

As shown on FIG. 8, the turbocharger 50 is further provided with a sealing ring 63 a mounted radially between the bushing 61 and the cap 58 and axially disposed between the compressor wheel 56 and the first rolling bearing 53, and with two sealing rings 63 b, 63 c disposed radially between the shoulder 52 b of said shaft 52 and the bore 51 a of housing 51 and axially mounted between the second rolling bearing 54 and the turbine wheel 55.

In the disclosed embodiment, the housing 51 comprises an axial cooling channel 51 c extending from a radial end surface of said housing 51 against which the cap 58 is mounted. The cooling channel 51 c extends axially further than the outer ring 59 of the rolling bearings 53, 54 and ends in the vicinity of a radial end surface of the housing 51 located on the turbine wheel 55 side. The cooling channel 51 c is closed by the cap 58. The cooling channel 51 c formed within the housing 51 is annular and radially surrounds the rolling bearings 53, 54 on its entire length. A cooling fluid (not shown), such as water, can be introduced into the cooling channel 51 c.

The housing 51 further comprises an axial drilling 51 d, acting as a lubricant reservoir, extending from a radial end surface of said housing 51 against which the cap 58 is mounted. The drilling 51 d ends in the vicinity of a radial end surface of the housing 51 located on the turbine wheel 55 side. The drilling 51 d formed within the housing 51 is annular and radially surrounds the rolling bearings 53, 54 and is provided with passages 51 e, 51 f made through the thickness of the housing 51. The passages 51 e, 51 f are adapted to cooperate respectively with a passage 59 e, 59 f made through the thickness of the outer ring 59 though which the lubricant contained in the drilling 51 d can flow by gravity towards the balls 53 b and 54 b.

As illustrated in FIGS. 8 and 9, the positioning means 64 of the intermediate sleeve 57 comprises an annular groove 64 a provided on the outer cylindrical surface (not referenced) of the first portion 57 a.

FIGS. 10 and 11, in which identical parts are given identical references, illustrate other examples of the positioning means 64 of the intermediate sleeve 57 for an external tool.

The positioning means 64 of FIG. 10 comprise one radial hole 64 b. As an alternative the hole 64 b can be made though the thickness of the intermediate sleeve 57, and a plurality of holes 64 b or through-holes can be made radially on the first end 57 a of the intermediate sleeve 57 and act as positioning means 64 for an external tool.

The positioning means 64 of FIG. 11 comprises a threaded portion 64 c.

It should be noted that the embodiments illustrated and described were given merely by way of non-limiting indicative examples and that modifications and variations are possible within the scope of the invention.

Thanks to the invention, the intermediate sleeve is easily disassembled from the shaft and the rolling bearings can be removed without being damaged during the disassembly procedure. Furthermore, positioning means located on an end of the intermediate sleeve extending axially further than the radial lateral surface of the first inner ring makes it possible to cooperate with an external tool.

The invention applies not only to turbocharger comprising an angular contact ball rolling bearing with a double rows of balls but also to turbocharger comprising other types of rolling bearing, for example rolling bearing having four points contact and/or with a single row of balls or with at least three rows of balls.

Finally, it has to be made clear that by a turbocharger it is also meant a waste heat recovery turbine, a turbocompound or a compressor. 

1. A turbocharger comprising: a shaft, a housing, a turbine wheel, and a compressor wheel mounted onto the shaft, and at least one rolling bearing located between the shaft and the housing and having: an inner ring, an outer ring, and at least one row of rolling elements between raceways provided on the rings, and wherein the turbocharger further provides at least one intermediate sleeve radially located between the shaft and the inner ring of the rolling bearing.
 2. The turbocharger according to claim 1, wherein the intermediate sleeve includes at least one end axially extending further than a radial lateral surface of the inner ring of the rolling bearing.
 3. The turbocharger according to claim 2, wherein the at least one end of the intermediate sleeve includes at least one positioning means adapted to cooperate with an external tool.
 4. The turbocharger according to claim 3, wherein the positioning means includes at least one annular groove.
 5. The turbocharger according to claim 3, wherein the positioning means provides at least one threaded portion.
 6. The turbocharger according to claim 3, wherein the positioning means includes at least one radial hole or opening.
 7. The turbocharger according to claim 3, wherein the positioning means provides at least one radial through-hole or through-opening, made through the thickness of the intermediate sleeve.
 8. The turbocharger according to claim 1, wherein the intermediate sleeve includes at least one axial slot provided axially on all the axial length of the intermediate sleeve.
 9. The turbocharger according to claim 1, wherein the intermediate sleeve has a stepped bore adapted to cooperate with a stepped outer cylindrical surface of the shaft.
 10. The turbocharger according to claim 1, wherein one end of the intermediate sleeve provides a shoulder.
 11. The turbocharger according to claim 1, further comprising a second rolling bearing mounted radially between the intermediate sleeve and the housing and having an inner ring, an outer ring and at least one row of rolling elements between said rings.
 12. The turbocharger according to claim 1, wherein the intermediate sleeve includes a first cylindrical portion in contact with the inner ring of the first rolling bearing, a second cylindrical portion having a diameter bigger than the diameter of the first cylindrical portion and a third cylindrical portion having a toroidal surface and forming an inner ring of a second rolling bearing having an outer ring and at least one row of rolling elements between said second outer ring and said toroidal surface of the sleeve.
 13. The turbocharger according to claim 12, wherein the intermediate sleeve has a stepped bore adapted to cooperate with a stepped outer cylindrical surface of the shaft.
 14. The turbocharger according to claim 11, wherein the first outer ring and the second outer ring form one unique outer ring.
 15. The turbocharger according to claim 1, wherein the intermediate sleeve is made of a metallic material. 